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= Two-Dimensional (2D) van der Waals (vdW) Dielectrics =

Two-Dimensional (2D) van der Waals Materials
Van der Waals (vdW) materials are two-dimensional (2D) crystalline materials composed of a single layer of atoms with strong in-plane covalent bonding and weak interlayer interactions. The out-of-plane weak vdW force is responsible for many unknown physical and chemical properties of these materials. Because of the weak nature of the vdW force, vdW materials can be easily exfoliated from their bulk (3D) composition down to a single layer.

2D vdW materials come in a variety of compositions, including hexagonal boron nitride (h-BN), Silicene, silicon carbide, transition metal chalcogenides, and rare earth oxides. This large spectrum of elemental variations in 2D vdW materials provides unique electrical, thermal, optical and dielectric characteristics with a wide variety of applications in electronic, thermoelectric, and optoelectronic devices.

Essential needs for 2D vdW Dielectrics
Ultrathin films are used to construct modern electronics such as memory, Field Effect Transistors (FETs), capacitors, and sensors. The future of electronic devices is dependent on continually decreasing gate length, although standards for these devices frequently demand thinner dielectrics with greater dielectric constants and lower leakage current.

One answer to this technological difficulty is to reduce the thickness of the high-k materials now in use. However, when the dimensions of 3D gate dielectrics in complementary metal-oxide-semiconductor (CMOS) transistors are reduced, issues such as excessive gate leakage current may occur. Using novel 2D vdW materials with a high dielectric constant as gate dielectrics are one potential approach to scale CMOS technology by reducing the equivalent oxide thickness (EOT) and minimizing power dissipation.

However, it is challenging to integrate 2D materials with a high-k gate dielectric with an EOT of 1 nm and a relatively low leakage current. Atomic layer deposition (ALD) is typically employed as an industry-standard deposition strategy. But, the non-uniform dielectric nucleation through deposition on 2D materials induce the dangling bonds. As a result, naturally terminated surfaces have become a substantial disadvantage due to the difficulty in forming covalent bonds between the oxide and the 2D substance.

In this regard, recent advancements in the field of 2D vdW dielectrics have sparked scientists' interest in their potential uses in CMOS technology. Relying on high dielectric constants and molecularly thin thickness, 2D dielectric capacitors offer unprecedented capacitance, allowing for efficient charge storage and minimizing current leakage. Moreover, novel 2D stable dielectrics with premier dielectric constants can be interfaced with Si at high temperatures to add superior functionality in the back-end-of-line or for other novel applications such as neuromorphic computing.